Mervyn John Williams (born 22 April 1940) is a New Zealand artist. He was an early exponent of Op art in New Zealand in the 1960s–70s. In 1990 he originated a style of illusionary abstract painting based on chiaroscuro, creating the impression of three-dimensional forms and textures on a flat canvas. Since 2009 he has used digital techniques in returning to an Op art style. Williams is almost unique amongst his contemporaries in New Zealand art for having embraced abstraction at the start of his career and exclusively throughout. His work is held in all major New Zealand public collections. A monograph by Edward Hanfling was published by Ron Sang in 2014 coinciding with a survey exhibition.